I'm not much of a hobby/modelling poster, so please forgive me if the following is old hat to everyone else.
I've been putting together a ridgerunner for the first time. Now, I like to keep my options open when it comes to vehicles, but magnetising the weapons arm on the back of the ridgerunner looked tricky, and fragile. And needed magnets smaller than the ones I had. So I came up with a different idea.
With just a little bit of trimming, you can configure the ridgerunner to switch between the mortar and one of the other options. And if you pick up another weapon arm (or magnetise the top, I guess), you can run to all three.
Here's what I did:
Stick the two support pieces onto the bed of the ridgerunner. Leave the locator pegs in place.
Cut a slot straight downwards from the hole on the weapon (on both sides). This allows the weapon piece to slide down onto the locator pegs.
It's a snug fit - this can be held upside down without any movement.
Repeat the process with the weapon arm. I've glued on the mining laser, and have picked up another arm for the missile launcher. The pegs provide sufficient grip to stop the arm sagging under the weight of the laser, so it still points forward nice and level.
No magnets, not a lot of extra work